Field of the Invention
The present invention relates to a zoom lens and an image pickup apparatus including the same, which are suitable for, for example, an image pickup optical system used in an image pickup apparatus such as a digital still camera, a digital video camera, a television (TV) camera, a monitoring camera, or the like.
Description of the Related Art
It is demanded that an image pickup optical system used in an image pickup apparatus be a zoom lens having a wide angle of field and high optical performance over an entire object distance from an object at infinity to an object at short distance. Hitherto, in order to obtain the high optical performance over the entire object distance with a small aberration variation during focusing, there have been known zoom lenses in which at least two lens units are configured to move during the focusing.
Of those zoom lenses, there has been known a zoom lens in which movement directions of the lens units, which move during the focusing, are changed depending on a zoom area to obtain high optical performance over the entire object distance.
In Japanese Patent Application Laid-Open No. 2012-83726, there is disclosed, in Embodiment 1, a six-unit zoom lens consisting of, in order from an object side to an image side, first to sixth lens units respectively having positive, negative, positive, positive, positive, and positive refractive powers, in which the second, fourth, and fifth lens units move during zooming. During focusing from an object at infinity to an object at short distance, the second lens unit moves toward the image side at a wide angle end, and moves toward the object side at an intermediate zoom position to a telephoto end. In addition, the fourth lens unit moves toward the object side at the wide angle end and the intermediate zoom position, and moves toward the image side at the telephoto end. Further, the fifth lens unit moves toward the object side over an entire zoom range.
In Japanese Patent Application Laid-Open No. 2007-93974, there is disclosed, in Embodiment 2, a four-unit zoom lens consisting of, in order from an object side to an image side, first to fourth lens units respectively having positive, negative, positive, and positive refractive powers, in which the lens units are moved during zooming. During focusing from an object at infinity to an object at short distance, the second lens unit moves toward the object side from an intermediate zoom position to the telephoto end. The third lens unit moves toward the image side at a wide angle end, and moves toward the object side at the intermediate zoom position. The fourth lens unit moves toward the image side at the wide angle end.
In recent years, it is demanded that a zoom lens used in an image pickup apparatus be able to focus at high speed, and have high optical performance over an entire object distance from an object at infinity to an object at short distance. In order to obtain such zoom lens, it is important to appropriately configure a zoom type, the number of lens units for focusing and their movement conditions, and the like. Of focus types, a focus type in which the lens units for focusing are moved in different directions in a predetermined zoom area of all zoom areas is small in aberration variation, with the result that the high optical performance becomes easy to obtain over all zoom areas and the entire object distance.
In order to obtain the high optical performance over all zoom areas and the entire object distance, selection of the plurality of lens units, which are moved during focusing, of the plurality of lens units forming the zoom lens, and appropriate setting of the movement conditions in each zoom area and the like become important. When those configurations are not appropriately set, the high optical performance becomes difficult to obtain over all zoom areas and the entire object distance while reducing the aberration variation. In addition, it becomes difficult to carry out focusing at high speed.